The present invention relates to an article comprising a polymeric substrate on which a layer of silicone polymer is assembled, at least one of these two components having been brought into contact with particles of titanium dioxide, magnesium oxide and/or zinc oxide, and water, before or after assembly of said article.
Silicone derivatives are commonly used in a certain number of technical areas such as the cosmetic, aeronautical, automobile or medical areas, for example for coatings of plastics or textiles, for airbags, prostheses, implants, dressings, etc. The silicone gels or gums notably offer the advantage that they can be assembled onto a large number of supports while being inert for the organism, thus avoiding any problem of toxicity when they are used in human beings.
When silicone derivatives are used as coating elements of supports or as a layer affixed on said supports, it is often desirable to reinforce their adherence to the substrates on which they are deposited, so that the products thus treated can effectively withstand physical stresses, moisture or temperature variations.
It is known, for example, to treat the surfaces of supports or siliconized surfaces by corona treatment to modify the surface energy of said support, so as to improve adherence with the silicone derivative during deposition thereof. However, the levels of adherence obtained by corona treatment are not always sufficient, and, in the case of siliconized surfaces, this treatment may even impair the adhesive characteristics of the silicone.
Thus, new technologies have been developed to improve the adherence between a polymeric substrate and a layer of silicone polymer, notably with the use of bonding primers.
Modification of the properties of adherence of siliconized surfaces by introducing bonding primers starting from the step of crosslinking of the silicone, directly within the reaction mixture containing the constituent precursors of the silicone, has notably been described in the literature. It has also been envisaged to deposit these bonding primers on a polymeric substrate, onto which the precursors of said silicone derivative will then be poured. In both cases, the end product offers levels of bonding that are slightly improved relative to a product that has undergone a corona treatment.
More recently, document WO 2005/051442 of the company Dow Corning Corporation proposed methods for improving the adherence of a silicone gel to the surface of a plastic polymeric substrate. This application teaches direct treatment of the substrate or silicone already synthesized by means of bonding primers of the titanate type, and preferably treatment of a silicone gel that has already been synthesized and crosslinked.
Thus, the use of bonding primers, notably primers of the titanate type, has been described for treating the substrate or the silicone derivative, either at the time of crosslinking, or once the substrate or the silicone derivative respectively has been synthesized or crosslinked.
However, more recently, application EP 2 053 161 of the company Dow Corning Toray partly adapted the teaching of application WO 2005/051442 with regard to the adhesion of a layer of silicone on a textile substrate. In this application, it was noted that bonding primers of the titanate type are unable to provide prolonged adhesion between a textile product and a layer of silicone, when these primers are incorporated in the reaction mixture constituting the future layer of silicone. The end product obtained by this method has inadequate levels of adherence, especially when it is submitted to large variations of temperature and humidity. This document recommends the use of bonding primers based on zirconium to ensure adhesion of a layer of silicone on a textile substrate.
Furthermore, the use of bonding primers of the titanate type poses problems both during use thereof and in the end product to which they are added. In fact, notably in order to avoid any contact with the water of the air, which could give rise to an anticipated chemical reaction, certain of these bonding primers, the most commonly used of which is titanium tetrabutanoate, are dispersed in an organic solvent. However, many problems of intolerance or even of toxicity are known, associated with the use of said solvents in the manufacture of an article such as that forming the subject matter of the present invention. It is also possible to use other types of bonding primers functioning in the aqueous phase, but whose results in terms of improvement of adherence are not satisfactory, and which moreover require the incorporation of additives (for example acetic acid) during use thereof and/or the application of a thermal treatment, said treatment being incompatible with the use of certain polymeric substrates.
Thus, the use of bonding primers of various types and notably of the titanate type causes many problems or complications associated with the application and use thereof. Moreover, the levels of adherence obtained by these treatments require further improvement.